HQRP Wick Filter for Holmes HM1100, HM1450, HM5100, HM1701, HM1910 Humidifiers + HQRP Coaster HQRP&reg; Humidifier Wicking Filter (Type A) Replacement + HQRP&reg; Coaster; Improves efficiency of the humidifier, traps mineral deposits from the water; Extended filter life with help of reinforced outer layer; Replace filter every 4-6 weeks, depending on usage and hardness of water; 2 weeks DOA replacement warranty!